Re: JavaScript over Lua as DSL

[Chris Marrin <chris@...>]

therandthem wrote:
> I would like to implement JavaScript over Lua.  This
> will be the full ECMA-262 specification with the
> ECMA-357 E4X XML entension.  Rather than create a
> traditional interpreter I will to use Lua to create a
> domain specific language (DSL) if that is possible.
>
> One method is Logix found at http://livelogix.net/. 
> Is the Logix approach, which runs on Python, necessary
> in Lua?  Does Lua's meta-mechanisms make this easier
> than the Logix approach?
>
> I am posting this because I do not have enough
> experience to do this very quickly on my own.  If
> others would like to work on this, please let me know.
>
> Here is my reasoning and motivation:
>   -The Lua language engine is very fast and it will
> get faster.  A co-worker recently commented, "Ruby is
> slow because it is interpreted."  I replied, "No, it
> is slow because it has a slow interpreter."
>   -Because Lua is fast it is a good candidate to use
> as a base for other (existing even) languages.  Lua is
> not Object Orientated so there is no awkward object
> model to object model translation.
>   -JavaScript will always be with us.  The Rhino and
> Spidermonkey engines are not fast.  When one needs to
> use JavaScript one should have fast JavaScript.
>   -Lua can do prototypes.
>
> So, that's it.  My ultimate hope is that a clear way
> to create DSLs in Lua will result from this effort. 
> If it does then I will move on to implement a DSL for
> PHP.  The ultimate goal is that any language with a
> slow interpreter can be recreated as a DSL over Lua.

I am doing precisely this. My project is called Emma3D 
(http://www.emma3d.org) and you can download the code base right now. 
The Javascript piece is in its infancy though so I don't think it will 
be much use to you yet. Our team is small and so there is no telling how 
long before we have a full Javascript interpreter.

So far I have a set of Javascript compliant object (Object, Array and 
Math, still working on Date) as well as an object model that allows 
these sorts of objects to be written in C++ or Lua with a full set of 
Lua interface classes in C++. Currently this is all wrapped up in the 
Emma3D engine, which runs its own Lua interpreter. But I am just 
finishing up the work to split out the object oriented piece into a 
separate library called Fusion. Fusion gets delivered as a dll (on 
Win32), is built with 5.1-alpha and is compliant with the 5.1 packaging 
model.

With Fusion you can go:

    require "fusion"
    local a = Array()
    a[0] = 1
    a[1] = "hello"
    print(a:join("--")

and so on. I will be making this available as source and binaries for 
Win32 within the next few weeks. We will also be porting to Linux and 
MacOSX, but haven't had the time for that yet.

I am also writing a Javascript to Lua translator, based on a Bison 
grammar file, which will translate the JS source into Lua source, then 
that will be compiled. I don't plan on implementing the entire 
ECMAScript 3 spec. There are a few things that are problematic. For 
instance:

- the with statement
- exception processing
- regexp constants

I will also be using a modified Lua interpreter. Most Javascript 
constructs, other than the ones I mentioned above, have simple 
translations to Lua. But some, like continue, would be really hard to 
do. So I will use the existing continue patch, as well as another patch 
that I uploaded to handle issues with the comparison operators.

Finally, the Lua ':' semantics are problematic from a Javascript 
standpoint. I am looking into this right now. I may end up having to add 
a bit of syntax to Lua and marking "member" functions that need to 
implicitly push a self pointer. I haven't figured it out yet, but 
hopefully it will be tractable.

Anyway, my work is probably too early to be of use to you. I just wanted 
to let you know that this work is available and to give you a heads up 
about the pitfalls!

--
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"As a general rule,don't solve puzzles that open portals to Hell"'